Perhaps the causation is reversed, and industries with terrible working conditions and low raises tend to attract unions to empower the workers to change those conditions?
People don't join unions if they are going to be worse off materially.
Tell that to anyone whose workplace unionizes against their wishes and lives in a "closed shop" state. (Yes, closed shops are illegal, but agency fees lead to essentially the same thing).
Being forced to pay a fee to a union that does not represent you and that you did not vote to join is absolute bullshit.
Of course they do. The difference is that they are tricked into thinking they won't be worse off by the union organizers pretending that it's unlikely everyone will completely lose their job.
How does that not sound coercive? A company saying "If you collectively bargain against us, we will punish you" sounds ok to you? You've been tricked out of collective bargaining by decades of anti-union propaganda, and now you're carrying water for capital.